Telephone-exchange system



G. A. E. LUNDELLL TELEPHONE EXCHANGE SYSTEM.

APPLICATION mm NOV; M1919.

Patented Dec-27, 1921.

3 SHEETS-SHEET I.

/nvem$or: ee/ye A/bm E Lunde G. A. E. Ll JNDE LL. TELEPHONE EXCHANGE SYSTEM.

APPLICATION F|LEDNOV= 1| 1919.

Patented Dec. 27, 192 1,

3 SHEETS-SHEET 2.

/n vemfor:

" e oryel/en lands G.'A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

Patented Dec. 27, 1921.

I APPLICATION FILED NOV=1. I9I9. 1,401,544.

3 SHEETS-SHFEI 3.

ln uentar ice/ye A/enilumel/ Aifys.

UNITED s'rArEs PATENT? oerce.

GEORGE ALBEN n. LUNDELL, or CHICAGO, ILLnroI's, nssmuon ro wnsrniin' ELEC- 'rarccomrm,- mconronnrnn, on NEW YORK, N. Y.,ncort1 om'r1o1v or NEW" YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. i Patented Dec, 27 1921 Application filed November 1,1919. Serial I'm- 835,181.

To all whom it My concern: J'Be it known that I, Gnonon ALnnN E.

LUNDELL, a citizen of the United States, re-

at Chicago, in the county of Cook -5 and .tate of Illinois, haveinvented certainy 'sidin new and useful Improvements in Telephone-f -Ex'change' Systems, of which the follow ing is a specification."

'I "l1 "s invention relates'to manually op" erated telephone systems in which the sysatem is divided into districts, that ,is tosay in which the subscribers telephone lines are divided into groups, and the lines of h group terminate atthe centra1. .*te op offices of the system. 0

It is the object of the present invent n; to provide an order circuit for th Se two operators, one in the answering: ofiice and the other in the called ofiiceywitlio'ut th necessity ofproviding-a pair of'wires tending between the two ofiices; I

vHeretofore it has been the practice mo 'erate such multi-oflice telephone systems over a call circuit or order were, described on page 487 of McMeen & Millers" Teleplze may, edition of 1912. The. call circuit, or

, order wire, according to the usual pracwt onal source of confusion. tending from one telephoneofiice toianother tice, is a separate pairbofi conductors ex;

telephone office, and is employed exclusively "by operators. When a subscriber originates a; call, for example, the operator," who an;

swers him, commonly" known as the sub:

scribers. or A operator, having obtained from him verbally the designation of the wanted subscribers line, depresses a call i circuit or order wire key corresponding to he oflice designation of the oilice in which he called line terminates. Thiskey places her, telephone set inoperative -connection overlthe order circuit to the telephone set of ;rthe." trunk 'orB operator, located at the trunk board in the-wanted olfice. Upon hearing the numerical-designation of a wanted linespoken, the trunk or B op e'rator responds'by verbally giving the number of an idle trunk which's'hechooses to use for the connection. She also insertsits erator meanwhile connects, by means-of a the subscribersoperator-just described. In thebusy hours'of the day, therefore, it oftenhappens, ;that sever'al' A operators depress 1the1r order'keys tothe same trunk operator at the same time, thereby establishing a 'tele-f v phonelconnection' from all of thei'r headsets to theordercircuit; "I he shuntinglefiect i f:

temptto pass orders simultaneouslyfshe use of the operators connected thereto, so that orders may be transmitted without con- ,fusionor loss'in transmis'sion} v :It is a further object of the present invencuit whereby the number o trunk may plug into the multiple jack of the wanted subscriber, assuming, of course, 'that the lled line is idle. -The subscribers ,or A

' assignedbythe 'trunkiop'erator, and the two subscribers are thus 'telephonically con"- nected;

In "large telephone 1 offices there are, .of course, a number of the suhscribersi, or A operators, havirtgrtliesame work to do as- .and since there isno way of, indicating to hese' A operators which of them sho iildi takef reference they all may speak, at the same elephone'systems to instruct t e trunk or B perator that'flwhen" several. A operator-s atshould disregard all of the orders, and wait for them to take turns.

1 This has lead to'a grat deallofconifusion, the poor grade of" transmission obtained; under such circumstances) being an addi-' An object of the present invention is'to PIfOVlClQ an order circuit for the exclusive tion ,to provide een-impr ved method of p choosing an idle trunk,..and toprovide acirbe indicated'to the operatoill It is a further obfectto provide a circuit for holding a telephone connection from the subscriber s operators headset to the order circuit until she takes upthe assigned trunk. Another object is to connect'the trunk operators telephone set to a't'runk circuit appearing at her position, "when a call comes in on-that trunk, so that she may receive orders over such-a circuit in the same man- I1er,as.she receives orders over the order sys temvpreviously used. A

It is understood that the disclosure herein set forth is only one of .a variety-of expressions which the invention is capable ofreceiving, and that the scope of the invention min" seriously aaeetsl the traii'smissiony ime.- "'It has been thepractice in the larger T is not to be determined by it, reference being had to the appended claims for that purpose. g

The invention 'will be understood more in detail by reference ,to the accompanying drawings wherein'is disclosed so much of .2, which is to be placed immediately to the rlght of Fig. 1, represents the part of the system located in each called ofiice, and Fig. 3, which is to be placed immediately 'below Fig. 1, represents a portion of the apparatus locatedin the calling ofiice, and includes the master switch bank, and in skeleton form the outgoing end of a' second trunk line c'ircuit. Fig. 4 shows in detail the construction of the master switch bank. Fig. 5 is a chart indicating the relation of the principal units of the system, and shows diagrammatically the calling and called subscribers', and various ofiices of 'a multi-office telephone system.- I

The secondary line switch 63 shown atth'e right of Fig. 1, represents a, trunk finding apparatus,;and for the purpose of setting forth the invention I show'a well known line switch of the type described in the British Patent #26301 of 1906. Said line switch comprises an electro-magnet- 44 with its plunger 48 and a bank-composed of a number ofbank spring sets, only one set being illustrated; The plunger 48 is pivotally fixed on armature 64 in such a manner that it can be rotated by the movement of the plunger shaft65. "In Fig. 3 there is shown the master switch306fwhich controls by the movement of the ratchet wheel 314 the plunger shaft 65 and a plurality of plunger armsf such as 48. Bank spring set 305 is a part of another bank spring set whose plunger arm is operated by the-same plunger shaft 65 as plunger arm 48'. The.

master switch 306 is adapted to control the,

ypositioning'of plunger shaft 65 to carry onthe next call.

The plunger arm 30 operable onthe energization of electr0-magnet 31 of the primary line switch is controlled by means of an additional master switch not shown.

It is to be understood that this master switch as well as line switches such as 31, controlled by it, are. mechanically independent of the master switch 306 and the line switch banks 305 and 63. The master switch 306 "comprises a motor magnet 313, an auxiliary relay 303 and a differential relay 304. The latter adapted to control the energization circuit of themotor magnet line switch'63 to seize an idle trunk.

313 which in turn controls the ratchet wheel 314. Referring to Fig. 4, the master switch bank 318 comprises'the individual contact points such as 308, 315, 316, 317, separated from conducting segment 310 by the insulating strip 402 and is so arranged that. when the wiper 312 engages the last contact point 316, and then on its next step is carried to the contact point 317 'on the right, the upper part of wiper 312 slides' on the spring 401. This provision is made in order that the wiper 312 in passing from the extreme left contact point 316 to the extreme right contact point 317 may not place the contact points such as 308 and 315 in connection with the conducting segment 310 whereby some interference might be experienced'by the master switch. The energization circuit for the differential relay 304 is controlled by the wiper 312 and whenever the said wiper 312 engages a bank contact having the guarding circuit closed the diiterential relay-304 is caused to operate and this in turn energizesthe motor magnet 313 until the wiper 312 is stepped into engagement with a bank contacthaving no guarding circuit closed. Incidentally the plunger shaft 65 is also rotated to carry all idle line switch plungers opposite the trunk line corresponding to the bank contact on which the wiper 312 stopped.

The electro-magnet 31, the plunger arm 30, and the bank spring set operated by the insulated ball 32 form part of the primary line switch cooperating with the secondary Only so much of the primary switch is shown as ,is necessary to an understanding ofthe invention, it being understood'that any suitable trunk finding device may be used, and that the one shown in the drawings is similar to the secondary above.

The subscriberat station 1, of Fig. 1, desiring to originate a telephone call to subscriber 200, Fig. 2, removes his receiver and closes thereby a circuit extending from grounded battery 2, the winding of line relay3, conductor 4, contact 5 of relay 6, conallaidle line switch plungefs opposite the nextidletrunk line in readiness to be seized ductor 7, substation 1, conductor 8, and contact 10 ot'relay 6, to ground, energizing thereby relay. 3, and closing the circuit of line lamp 11 at thecontact 12. Relay 13 is a pilot relay common to a plurality of line lamps 11 forclosing the circuit'of a pilot lamp (not shown) to indicate to the operator when anyof the associated line lamps are burning. The subscribers 01181'2113011113011 noticing thatline lamp 11 is lighted chooses plug 14 of one, of those in her position which are not at the moment engaged, and inserts it into ack\15, establishing thereby a circuitfrom' the. grounded battery 16 through supervisory signal 17, resistance 18, plug 14,

line switch 63 described -windin'g ofrepeating coil 21, for-supplying .10

ing the relay'6 "and opening contacts and. 10. This causes line relay 3 to become re-' leased and the line lamp 1-1 is thereby ex-' battery for operating the substation. transmitter, and for operating relay '22. The operation of relay 22 closes at its; front contact i a shunt circuit by way'ofconductor 23', and

nection from her telephoneset' 26 i- ,hand windings of repeating.,

thus'inductively to the call I the plunger27 closes vthereby contact 28 establishing' a" circuit for. operat ng .relay resistance 24 around supervisory operator. The operator now closes number of thesubscriber 'w The resistance 24 is of such val illumination will not be noticeable ing key 25 and establishes a teleph She ascertains over-this circ The, subscribefis operator n w, depresses 66 andforistarting a'trunk finding operation which will now 'be described .in detail.

The plunger-.30 of the-primary switch, as described insthe, British Patent 26,301 of 190(),always stands before the set of springs,

- associated with an idle connecting circuit,

' forward forcing theins'ulating ball 32 there its cooperating contact.

of between the innermost springs of the set whereby each of the foursprings of'theset is forced outwardly into engagement with The ,lead 33assow ciatetl, through-contact 34 with primary gels of: the. group are moved to 'a position,

known means-all of-the remaining idle plun- Lbefore thespringsassociated with the next lead 36 through. the normally closed contact rest to the next, the circuit is opened at contact 37 so that no finder mechanism can. be

actuated during this interval.

Upon the closure of contact 28, as hereinabove described,current flows over the fol flowing circuit: battery 38, contact 37, con-' ductor 36, left hand winding of electromagnet 31, contact springs 40and 41, conductor 42, contact 28, to ground, causing the,

armature of electro-magnet31 to be attracted, and the plunger to force the in sulatin r ball 32 between the springs'of the set befire which the-jplungeris resting.

lainp 17 ,as to re-j. duce the current through superyisory lamp? 17 sufficiently to dim it to the point'where ger stands. As has been pointed out, the electro-magnet 44 and. the set of springs as Contact is disengaged from contact 41 and a circuit is established through the right hand winding of magnet 31, whereby the plunger arm 30 is held in itsoperated position independent of contact 37. This circuit is as follows: Battery 67, right hand 'winding of magnet 31, contact 68, conducthe key 27. This energizes the'electro-mag- .net 44, and by attracting. its armature 64,' forces the plunger 48 between the innermost springs of' the set before which this plunsociated with plunger 48, as well as the spring set 305 and .the master switch 306,

i form part ofa secondary trunk finder mechanism'similar to the primary line switch and .to that shown in British Patent 26,301 of ating ball 50 having been forced The ins. inQbet'weI vthe associated set of springs, 00" '51 closes a l circuit ground to con- 307,- contact 308, wiper 312, conductlatev 310, winding of -relay"303,'-1eft Winding of differential relay 304, to ery';31l,'and relay 303 is thus operated v "andjholds contact 302.0pened so long as the and upon sufficientenergia'ation of the lem; tro-magnet 31 this plungerwill bedra'wn 5.

master switch arm .312 is contacting with such terminals as 308 of busy'trunksu The :Lmagnet. 44 remains .ener ized, and .the

plunger arm 48 remains -'1n the operated 1 position, b'yyirtue of a circuit through the right hand winding .of. the magnet 44, contact T0, conductors 46 and 47,-contact 43 ',0f the primary lineswitch, contact 28 to switchf'gcontact35, leads to the master switchq as shown in-the above'mentioned British patentj-i whereby through action of well ground, independent. of the contact 302.

.The operation of relay" 303- opens its contact' 302 and 1 disconnects the 1 battery 301 from the-conductor 320 and fromthe left hand windings ofall line switch magnetswhoseplnn'g'er.v arms are associated with the plunger shaft 65. The operation of the differential relay 304 closes the circuit of thein'otor'magnet 313 and the master switch 306. together with the plunger shaft is "rotated until; the wiper, 312 contacts with a nongrounded contact, that is, with the contact of' anidle trunkg 'such as .321. i

The operation of magnet 44, also closes. thecontactll04, for operating relay 85, which thereupon operates and locks itself through its own left hand front contact and resistance 105 to ground at the left hand back contact ofrelay 87." Relay 66, and magnets31 and 44 are now grounded,- by way of the left hand front contact of relay85, independently of "the contact 28 of the key and the operatornow removes her finger from the plunger 27. Her head set nevertheless remains connected to the order circuit as before.

The operation of electromagnet 44 causes the closure of contacts 52 and The operation of electromagnet 31 causes the closure 7 of contacts 54 and55. A circuit is now established from battery 56 through righthand winding of retardation c011 57, conductor 58, contact 55, conductor 60, contact 53, conductor 180, lower left hand winding of repeating coil 201, of Fig. 2, conductor 202, left hand winding of relay 2033, conductor 204, upper left hand winding of repeating coil 201, conductor 178, contact 52, conductor 61, contact 51, left hand winding of retardation coil 57 to ground, energizing the relay 203 of Fig. 2.-

Acircuit is now closed from battery 205, lamp 287, conductor 206, contact 207 of relay 203, conductor 208', back contact210 of relay 213, conductor 211', back contact of relay 212, conductor 213, winding of relay 2let, contact 215 of this, 're1ay,-conductor 216, resistances 217, back contact 218 of relay 221 to ground.- The consequent operation of relay 214 connects the operators telephone set 223 into conversational relation with trunk line ,178 and 180, over a circuit including the battery 238, the lower.

right hand winding of repeating coil 201, winding of supervisory relay 236, conductors 225, 235, contact 227 of relay 214, condenser 228. winding 230 of an induction coil, operators receiver 234:, conductor 233, contact 226 of relay 214, conductors 231 and 221, upper right hand winding of repeating coil 20.1 to ground 230.

Relay 211 remains in its operated position independent of contact 218 by virtue of a circuit from battery 205, lamp 237,

conductor 206, contact 207, of relay 203, conductor 208, contact 210 of relay 2123, conductor 211, back contactof relay 212, conductor 213,, winding of'relay 211, left handfront contact of this relay, conductor 220, winding of relay 221, contact of key 267-to ground. Accordingly relay 221 opcrates and opens at its back contact 218 the energizing circuit ofv all relays corresponding to'relay 21 1 associated with the same operators head set 223, one of these other relays being shown .as 614:; no such other i relay can therefore be energized since no scribed, that trunk conductors 178 and 180 cannot become connected to any A operator other than the one described, since a guarding ground has been placed upon the master switch bank contact 308 as soon as these conductors were seized. The talking circuit therefore now available for.their individual and exclusive use while passing the order for the connection.

The complete order circuit may be traced as follows: The operators induction coil 26, conductor 72, contact 73, of the, relay 66, which as described above is in its-operated position, contact 54 of the primary line switch, conductor 61, contact 52 of the secondary line switch, trunk conductor 178, upper left winding of the repeating coil 201, condenser 253, lower left winding of the repeating coil 201, trunk conductor 180, c011- tact -53 of the secondary line switch 63, conductor 60, contact'55 of the primary line swtch', contact 74 of the relay 66, condenser 75, the operators head receiver 76 to the, induct-ion coil 26, the primary circuit of which is closed through the operators transmitter 77 in a well known manner. In inductive relation with left hand windings of repeating coil 201 in the circuit described, are the right hand windings of the same repeating coil and a circuit extends through them as follows: Grounded battery 238, lower right hand winding of repeating coil 201, relay 236, conductors 225, 235, contact 227 of relay 211, which it will be refrom the A operator to the B operator is tively with the secondary winding 230 is in circuit with the B operators transmitterin a well known manner. The telephone'set of the A operator is thus opcratively connected with the telephone set of the B operator. The A operator gives verbally over tlns conversational cn'cult the numerlcal designation of the wanted line. It is, of course,

unnecessary for her to give the ofiice designation since her selection of the key 27 caused a trunk to the selected ofiice to become connectedwithher telephone set. The 15 operator makes acknowledgement by giving the trunk number of the circuit over which she is speaking, the illumination of the lamp 237 in the circuit previously described indicating to the 15 operator: this trunk number, and its being necessary for -her only toglance at the number plate associated with the lighted lamp to determine the proper number to give.

Thus the A operator has been apprised of the trunk number and she inserts the plug 7 8* into, the "jack 80 of the designated trunk. A circuit is now established from battery 81, through supervisorylamp 82, resistance 83,

lug 78, jack 80, winding of relay 84 to ground, lighting lamp 82 and Operating ire- .lay 84. The latter in turn causes the operation of relay 87 over the circuit: battery 88,

' tact 51 ofsecondary line switch 63.

Relay 87 also closes, at its contacts 92 and 93, the following circuit: Grounded battery 80, plug 7 8, conductor96, upper-right. hand winding of repeating coil-21 to .grou d,

. te 56 ,orrfromthe batter-y20.

tential on the sleeve of the 'jack trunk line con uctor 180,lowerleft;wind1 g I, a of repeating coil 201, conductor 202,;3le

t u i i o v j upiper left hand w1nd1ng of repeatingcoi the plug78 into the jack 8O si -mass; .s'he; has received the number of, th trunk coil'21, the marginal supervisory relay; conductor 95, lug78, j'ack-80,-:contab hafnd winding of relay 203, oonductor".204,

20lgjtrunk line conductor 170,,contact .93,"

p'ro\ 7iding a circuitfifor holding t e; 03Qn8rgized independent of the bat-y twill be seen thatthe A operateiflpan is from 'the'B operator, and that the-Pre a isflheld energized equally well fr'onrth a he operator picks up the plug 46 sociated with the lightedjsupervisor and tests the called subscribersline n: usual manner. A busy line; will potential will cause current tQiifl.

plug is touched to the jack; C'oiiductor 24l,

contact 242 of the relay 243, conductor244,

bang-wees, it being understood that. the battery 265 is the same as that shownat 266. 'The release of relay 256, as the result of winding 246 to ground. -Winding 246 is inductively related to thewinding'230, and the fiow of current through it induces a-curf rent through the latter,1 aiul.also*through the operators; receiver 234, indicating to the. operator that the called line is busy. Assuming that thecalled line is idle and that no current'flowslin this circuit, and that.

consequently no clickisreceived by the operator when she tests thejack, she inserts the plug 240 into the jack 247. :(Jurrent now:

flows from grounded battery-205 through the J lamp 237, conductor 248 ,winding of relay 243, conductor 250, plug 240, jack 247, con;

:ductor 251, winding of cut off relay 252,

operating relay 243, and disconnecting the i busy test winding 246 from this circuit. The

94 thefbattery at 205 ;ductor 213' for a pur l, afterbe fully set forth.

operation of relay 256 closes a cir- ,eult from a source of ringing current 257 through the winding of relay 254, contact 3 95' "hitherto received through the l l'fetardation coil'57.

circuits of relays 214 and 221 are broken at the contact 210 of relay 243, and the release of relay 214 disconnects the operators telephone head set 223 from conductors 231 and 235. The release of relay 221 makes the set avallable for use in 'connectionwithother relays corresponding 60 2111 Qf,tl1- other 256, 'to-grounded battery operating relay 25.6, and also through the winding of relay 212 to grounded battery. The resistance'of,

I h the winding of relay 256 is of such value as 20, lower right hand winding of repeat ng to cause the extinguishing of the lamp 237, being the same as that howmat 266:

ask contact the} circuit by way of 2533 ofrelay256, conductor 260, plug 240,

,Ljack 247, conductor 261, the substation 200,

conductor 262, the jack 247,.the plug 240,

the conductor 241, right hand front con act of the relay 243, conductor 263, front 'ontact 264, to ground." The bell at the subt"'t'on2 0 0 is operated and when the called u scriber respondshe introduces into the "rough his transmitter. This causes an ncrease of .current- 1n thecircuit of relay clay, and the-opening of the contact of this relay rem'ov'es a short circuit from around [the winding of-relay255 ,.and causes current tolfiow therein; The' consequent operation 1 the following circuit when thBtlPiOf-Ttlle ofre'lay 255 causes its front contact to be closed, andfa {short circuit then is placed aroundthe windingof relay 256 through the the short circuit of lts winding, causes contacts 264 and 258 to open disconnecting thereby the source of ringing circuit from the subscribersline and restoring relay 254 to normal. A conversational circult is now closed for operating the subscribers transconductor 225, back contact of relay 256, conductor 260, plug 2'40,jack247, conductor 261, sub-station 200', including the transmitter therein,c6nductor 262, jack 247 plug pose which will here-- ub station circuit the low resistance path.

54, just;described,suflicientto operate said 4 lefthand front contact of relay 243, baclrcontact of relays 254 and 255, throughthe winding of relay he Perm-6011M y 219'. pens at its "fpea'ting coil 201, supervisory relay 236, the i i 240, conductor 241', right hand front contact of relay 243, conductor 263, back con-' tact of relay 256, conductor-224, upper right hand winding of repeating coil 201 to ground 230.

The operation of relay 236 closes the circuit of the low resistance right hand wind ing of relay. 203, and. thus increases the flow of current'over trunk line conductors 17 8 and 180 sufiiciently to operate the marginal relay 94. The operation of relay 94 closes a shunt circuitaround lamp 82 through the resistance coil 103, whereby the lamp 82 is extinguished. Subscribers l-and 200 .carry on their conversation and upon restoring their receivers to the switchhooks at its termination, cause the release of relays 22 and 236, the latter in turnby open ingthe low resistance circuit of the right hand winding of relay 203 causing relay 94 to retract its armature. The shunts 24 and 103, are therefore removed from the supervisor lamps 1 8 and 82, causing them to burn brightly and thus toindicate to the operator thatthe conversation is finished.

The operator pulls-out plugs 14 and 78, restoring relays 6 and 84 to normal. The

'4 release of relay 84 cause in turn the release of relay 87, and this opens the circuit by way of conductor 104 to the master switch bank 318, and frees. the contact point 308 from ground, so that trunk conductors. 178 and 180 become available for use on a subsequent call. The removal of plug 78 also causes the release of relay 203, and thi in turn removes the shunt around lamp 237. The increase in current in the lamp 237 causes it to light, indicating thereby to the B operator that the plug 240 should be disconnected. Relay 255 is released upon the release of relay 203.; The operator accordifigly removes the plug and relay 243 retracts its armature. In case the A operator does not understand or remember the number of the trunk, and therefore refrains from plugging into the designated trunk, the response of the called subscriber 200 will be heard in her head set since electroanagnets 31 and 44 andrelay 66 will not then have been released and the conversational circuit will thus connect the called subscriber with the A operator instead of with the calling subscriber; She may then advise the called subscriber that an error occurred and request h m to restore his receiver to the hook and she may disconnect the connection by' operating the disconnect key 97. This connects the battery 98 through the resistance coil 101 in shunt with the winding of relay 8.5, itbeing understood that the battery 98 is the same battery as that shown at 102. The resistance 101 is of such value as to re d'uce the current-flow through the winding of the relay 85 sufficiently to cause it to release. The restoration of the relay 85 to normal, under uch conditions. removes the ground supply to electro-magnets 44 and 31, causing them. to restore their plunger-s 48' signal'in front of the B operator to be light-' ed, whereupon the B operator pulls down the plug 240. The A operator can now set up a newconnection in the same manner as before. i

Should the B operator inadvertently pull down the plug 240 while conversation is being carried on over it her telephone set will not become connected with the corresponding trunk circuit, the circuit of relay 214 being held open at the back contact of slow release relay 212. Relay 243 releases when the plug is removed under these conditions, and a circuit is closed from battery 205, lamp 237, conductor 206, contact. 207 of relay 203, conductor 208, the contact 210 of relay 243, conductor 211, right hand armature front contact and winding of relay 212 to ground. Lamp .237 is caused to burn brightly by the current matic representation of the connecting apparatuses of the A operators position, one of which is also shown in Fig. 1. 200, 506, 507, 508, 510, 511, 512, and 513, represent called subscribers stations arranged in two groups, the group comprising stations 200, 511, 512, and 513 being provided with artrunk board 504 which comprises the apparatus shown at the left hand side of Fig. 2; subscribers stations 506, 507, 508, and 510 are provided with a trunk board such as 505, and it is understood that this board may be wired the, same as At the trunk board 504 there is provided the trunk opcrators set 234, and at the trunk board 505 there is wired the trunk operators telephone set 534, the details of the connection .of these telephone sets being shown in Fig. 2, and the operation thereof having been. described .above. Connecting the A operators board 502 with the B operators board504 are several pairs of trunk conductors178 and 180, being one pair, and 678 680 being another pair. Connecting the A operators board 502 with the trunk operators board 505 is a pluralityof trunk conductors, one pair of which is designated 57 8, 580. The pair 678, 680, and the pair 578, 580 correspond in, functions to the pair 178, 180, and the details of wiring are similar to those for 17 8, 180. The A operators board 502 is provided with the key .27, and this key to trunk board 505.

27 ca-uses the operation of trunk tinder 63 for selecting an idle trunk line extending to the trunk ban-acne Another key 527 is provided for causing-the actuation of trunk finder switch scawvl'uch automatically selects an idle pair of trunk connections extending The wiring of the key 527 and the trunk finder 563 corresponds to that of key 27 andtrunk finder-:63, and-it will be readily understood thathy manipulation of the key 27 the operator can cause the seizure of an idle trunk to office 504and that by manipulation of key 527 she may initiate the operation of trunk finder for select ing an idle trunk extending to trunk board 505. In Fig.5. there is indicated the connection from the trunk operators telephone set 234 through contact of relay 214 to the pair of trunk conductors 17S and'180 and the corresponding relayfil l associated with the pair of trunk line conductors 678 and 680. By

: means ofthese' relays 214 and 614 the trunk 'operators head set becomes connected with their assoc'iatedtrunk line conduc rs. The operators head set 534 at trunk board 505 is wired in a similar manner through the con- 1 tacts of relays, one of which is shown at 514:

' swering operator-ls board, called subscribers; l nes arranged in groups, a trunk board foreach group, a pluralltyof trunk lines ex j from the answering board to each for connecting thishead set to a thinker;- 1*

tending to trunk board 505. p p I cla1m as myinvention:

1. In a telephone exchange system a tendin trunk hoard, an operators telephone set at each of said boards, a key at'the answering board fo'r 'each group of trunk lines, automatic selecting means actuated by the opera- Ction' of thekeyfor seizing an idle trunk line iofi gthe group, an ordeiflcircuit for operaeach group, a plurality of trunk lines ex tively connecting the answering telephone set and a trunk telephone set over the sea 45 tendin from the answering board to each trunk card, a key at the answering board for each group of trunk lines, automatic selectingmechanismactuated upon the operation key.

of a key for seizing an idle trunk line of the grouppiand a' locking relay for 1naintaining automatic selecting mechanism in its actuated ,position independent of the 3.- In a telephone exchange system ananswering operators board, a trunk operators board, trunklines, extending from one board to the other, automatic selecting means for SBIZlDg an dle trunk, a telephone set for each group of trunks, means individual to each trunk for operatively connecting a trunk to a telephone set, and means responsive to the initiation of a call on one trunk for rendering inoperative the connecting means of the group.

, 4. In a telephone'exchange system a calling subscribefls line, an answering opera-- tors board, an operators telephoneset thereat, called subscrlbers lines arranged 1n groups, a trunk board for each group, a plurality-of trunk lines extending from the an swering board to each trunk board, manual connecting means for connecting the calllng matic selecting means for operatively 0on necting the A operators boardto an. idle.

subscribers lines with a trunk line, auto trunk independent of said manual connect 3 ing means, and a relay for maintaining said automatic selecting meansin its operative position, and means for releasing said relayupon the employment of said manual connecting means. i r 5. In a telephone exchange system a calllng subscribers line; an answering operators board, an operators telephone set thereat, called subscribers lines arranged in groups, and a trunk board for each group, a -"plural1ty of trunk lines extending from the answering board to each trunk board, man ual connectlng means for connectlng the callingsubscribers llnes with a trunk l1ne,automatic selecting means 'for operatively connecting the answering operators board to an idle trunkindependent of said manual connecting means, a relay for maintaining said automat ic selecting means in its operative position, meansfoperated by the employment of said manual connecting means for releas- "ingsaid relay,-and a conversational circuit for operatively connecting the answering operators telephoneset with a called sub:

scr-ihers line. I

- 6.,In a telephone exchange system an op? erators board, anrop'erators telephoneset tending froin one board to. the other, auto'-' matic selecting mechanism for. operatively connecting to an idle trunk theA operators telephone set, a B operators telephone set,

means individual to each trunk line operatlve upon seizure ofsaid trunk line for cona lockin relay for each trunk adapted to disable the last mentioned means. r 7 In a elephone exchangesystem an anboard, trunk lines extending from one board to the other, automatic selecting means'for each group of trunks,a relay individual to each trunk for' o'peratively connecting a thereat, a B operators board, trunk lines ex necting the B telephone set to the trunk, and i uswering operators board, a trunk operators seizing an idle trunk, a telephone set for trunk to a telephone set, and a locking relay adapted to open the circuit of said connecting relay.

8. In a telephone exchange system, an answering operators board, called subscriberslines arranged in groups, a trunk board for each group, a plurality of trunk lines extending from the answering board to each trunk board, a key atthe answering board for each group of trunk lines, automatic selecting means actuated upon the trunk, means for initiating the operation of said automatic mechanism and means-for maintaimng sald mechanism in its actuated position independent of said initiating means.

10. In a telephone exchange system, a calling line, an A operators board, a telephone set thercat, trunk lines extending from said board, means for selecting an idle trunk line, means for connecting said calling line to said idle trunk line, a start circuit for said selecting means operated independent of saidconnecting means and means for maintaining the selecting means in its operated position.

11. In a telephone eychange system, a calling line, an A operators board, a telephone set thcreat, trunk. lines extending from said board, means for selecting an idle trunk line, means for connecting said calling line to said idle trunk line, a start circuit for.

said selecting means operated independent of said connecting means and means independent of said start circuit for maintaining the selecting means in its'operated position. In testimony whereof, I hereunto set my hand.

GEORGE ALBEN E. LUNDELL. 

